(Netplay/Vita) Enable partial LAN discovery (#14222)

Makefile.griffin

@@ -345,6 +345,7 @@ else ifeq ($(platform), vita)
    HAVE_7ZIP                := 1
    HAVE_VITA2D              := 1
    HAVE_NETWORKING          := 1
+   HAVE_NETPLAYDISCOVERY    := 1
    HAVE_OVERLAY             := 1
    HAVE_VIDEO_LAYOUT        := 0
    HAVE_MATERIALUI          := 1

Makefile.vita

@@ -75,6 +75,7 @@ else
 	HAVE_VITAGL		:= 0
    endif
 	HAVE_NETWORKING		:= 1
+	HAVE_NETPLAYDISCOVERY	:= 1
 	HAVE_SOCKET_LEGACY	:= 1
 	HAVE_MENU		:= 1
 	HAVE_MENU_COMMON	:= 1

network/netplay/netplay_frontend.c

@@ -8550,7 +8550,9 @@ static bool netplay_pre_frame(netplay_t *netplay)
    {
       settings_t *settings = config_get_ptr();
 
-#ifdef HAVE_NETPLAYDISCOVERY
+/* Vita can't bind to our discovery port;
+   do not try to answer discovery queries there. */
+#if defined(HAVE_NETPLAYDISCOVERY) && !defined(VITA)
       if (!netplay->mitm_handler)
       {
          net_driver_state_t *net_st = &networking_driver_st;